Oracle Blog

Steffen Weiberle

Using IPMP with link based failure detection

Solaris has had a feature to increase network availability called IP Multipathing (IPMP). Initially it required a test address on every data link in an IPMP group, where the test addresses were used as the source IP address to probe network elements for path availability. One of the benefits of probe-based failure detection is that it can extend beyond the directly connected link(s), and verify paths through the attached switch(es) to what typically is a router or other redundant element to provide available services.

Having one IP address (whether a public or a private, non routable) per data link and also the separate address(es) for the application(s) turns out to be a lot of addresses to allocate and administer. And since the default of five probes spaced two seconds apart meant a failure would take at least ten (10) seconds to be detected, something more was needed.

So in the Solaris 9 timeframe the ability to also do link based failure detection was delivered. It requires specific NICs whose driver has the ability to notify the system that a link has failed. The Introduction to IPMP in the Solaris 10 Systems Administrators Guide on IP Services lists the NICs that support link state notification. Solaris 10 supports configuring IPMP with only link based failure detection.

you will notice that two of the three interfaces have no address (0.0.0.0). Also, the data address is on a physical interface on bge1. At the same time bge2 has the 0.0.0.0 address. On the failure of bge1,

So a simple case for the use of IPMP, without the need for test addresses! Other IPMP configurations, such as more than two data links, or active-active, are also supported with link based failure detection. The more links involved, the more test addresses are saved with link based failure detection. Since writing this entry I was involved in a customer configuration where this is saving several hundred IP address and their management (such as avoiding duplicate address). That customer is willing to forgo the benefit of probes testing past the local switch port.

Hi Arul, as long as you only assign one of the interfaces to each zone, things will work. For an active/active configuration I also like assigning half of the zones to one interface and the other half to the second.

Current setup is running 2 NIC interface with active-passive ipmp setup. I am planning to add 2 more Interfaces to the same IPMP group(as 11 zones so N/W load will be high) and distribute all 4 I/Fs to the zones. Each zone will get single but different interface from the same IPMP group.